Chemical dispenser

ABSTRACT

The disclosure describes a specimen dispenser in which first and second syringes are used to dispense a sample liquid and a reagent liquid. The inlet orifice of the second syringe is connected to a second end opening of the first syringe through a three-way valve so that the first syringe is purged by reagent liquid each time a dispensing operation is completed.

United States Patent 91:

Liston June 18, 1974- [22] Filed: May 3, 1973 [21] Appl. No.: 357,065

Related US. Application Data [62] Division of Ser. No. l33,08l, April12, 197i,

abandoned. I

[52] US. Cl 222/1, 23/259,73/423 A, 222/145, 222/309 [51] Int. Cl. G01f11/16 [58] Field of Search 222/145, 309, 386, 1; 73/4256, 425.4 P, 423A; 23/259 [56] References Cited v UNITED STATES PATENTS 3,l38,294 H1964Coulter 222/145 as; Ass

3,484,207 12/1969 Anthon ..222/309X Primary ExaminerStanley H. TollbergAssistant Examiner-Thomas E. Kocovsky Attorney, Agent, or Firm-Molinare,Allegretti, Newitt & Witcoff [5 7] ABSTRACT 10 Claims, 16 DrawingFigures DISCHARGE POSITION aalimas PATENTEDJuu 18 m4 saw 03 or w mNN NRN

www Qww m 3m QM WNN CHEMICAL DISPENSER RELATED APPLICATION Thisapplication is a division of my application Ser. No. 133,081, filed Apr.12, 1971, entitled Digital Chemical Analysis Apparatus," now abandoned.

BACKGROUND AND SUMMARY OF THE INVENTION This invention relates tochemical dispensing apparatus and more particularly relates to apparatusadapted to dispense and mix minute quantities of fluid.

In order to rapidly analyze the concentration of a particular substancepresent in a chemical specimen, such as blood, chemists are placingincreasing reliance on various types of machines. Such machines devisedin the past may be divided into at least the following types:

I. Blood gas analyzers;

2. Prothrombin time determining systems;

3. Flow systems;

4. Electromechanical methods not related to color imetry; and

5. Monochromatic servomechanism systems.

Although such machines have somewhat reduced the labor involved inperforming chemical analysis, they have exhibited many deficiencies thathave limited their overall usefulness.

For example, prior art specimen dispensers used with the machines aredifficult to load and clean.

According to a principal feature of the invention, applicants dispensercomprises two cavities, such as sy ringe barrels, each fitted with meansfor changing the volume of the cavities, such as plungers. Byinterconnecting the barrels and plungers in the manner describedherein,the applicant has found that the dispenser will mix sample and reagentfluid with a degree of accuracy heretofore unattainable. In addition,the dispenser has a selfpurging feature which significantly reducescontamination and also reduces the volume of sample and reagent fluidrequired for each analysis.

; DESCRIPTION OF THE DRAWINGS These and other advantages and features ofthe present invention will herein after appear for purposes ofillustration, but not of limitation, in connection with the accompanyingdrawings, in which like numbers refer to like parts throughout, and inwhich:

FIG. 1 is a perspective view of a preferred form of apparatus made inaccordance with the present invention;

FIG. 2 is a cross-sectional, fragmentary, partially schematic viewshowing the cuvette assembly, carrousel assembly, cycling apparatus,positioning apparatus, and a portion of the analyzing apparatus of thepreferred embodiment;

FIG..3 is a front elevational view of a preferred form of a dispenserassembly made in accordance with the present invention, with the hoodand cabinet thereof removed, the probe holding assembly of the dispenserassembly being positioned over a test tube of the carrousel assembly;

FIG. 4 is a top plan view of the apparatus shown in FIG. 3 in which theprobe holding assembly is positioned over thecuvette assembly;

FIG. 5 is a side elevational view of a preferred form of a probeassembly used in connection with the dispenser assembly;

FIG. 6 is an enlarged, side elevational view of a preferred form of aprobe nozzle used'in connection with the probe assembly;

FIG. 7 is an enlarged, top plan view of a valve and a microsyringe shownin FIG. 3;

FIG. 8 is an enlarged, fragmentary, crosssectional view of thelike-numbered encircled portion of FIG. 7;

FIG. 9 is an enlarged schematic diagram of the syringes and valve shownin FIG. 8 during a discharge mode of operation;

FIG. 10 is an enlarged, fragmentary, schematic diagram of the valveshown in FIG. 14 during a charge mode of operation;

FIG. 11 is a fragmentary, side elevational view of a portion of thedispenser assembly shown in FIG. 3;

FIG. 12 is a front elevational view of the removable plate of thedispenser assembly, together with the apparatus connected thereto;

FIG. 13 is'a fragmentary, side elevational view similar to FIG. 16 andshowing additional apparatus used to operate the dispenser assembly;

FIG. 14 is an enlarged exploded view of a portion of the apparatus shownin FIG. 13;

FIG. 15 is a schematic diagram of a preferred circuit used to controlthe dispenser assembly; and

FIG. 16 illustrates certain signal waveforms produced by the circuitshown in FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a preferredsystem for analyzing chemical specimens made in accordance with thepresent invention basically comprises a cuvette assembly 30; a carrouselassembly test tubes 138; a dispenser assembly 200; and a console 502that includes analyzing apparatus, a processing circuit and a memory.

Referring to FIG. 2, cuvette 30 comprises a plurality of compartments,such as compartments 67 and 83. Compartment 83 comprises sidewalls 34,40 and a bottom-wall 48. Spacers 58 (FIG. 1) are fitted betweensidewalls 34 and 40 to enclose the compartment. Compartment 67 isconstructed in a similar fashion.

Referring to FIGS. 1 and 2, assembly 110 is provided with a movablepositioning platform comprising a cylindrical skirt 132 and aring-shaped test tube retainer 134. The retainer comprises a horizontalring member 136 that is provided with holes for receiving 32 test tubescommonly designated by the number 138, and including exemplary testtubes 140, 141. Each of the test tubes lies along a radius common to acorresponding cuvette compartment. The retainer also comprises avertical ring-shaped retainer 142. According to the preferred embodimentof the invention, the test tubes are used to hold chemical samples priorto the time they are mixed with a suitable reagent to form a specimenfor analysis. The tubes are biased against retainer 142 by resilientspring clips, such as exemplary clips I43, 144. The clips are mounted onskirt 132.

Positioning platform 130 also comprises a raised, ring-shaped portion146 that carries on its underside a circular positioning member 148bearing detents. Member 148 is provided with one detent opposite eachtest tube and corresponding cuvette compartment, so that each specimenmay be accurately located in a predetermined analyzing position duringthe analysis procedure. The entire positioning platform is rotatablymounted on platform 115 by means not shown. The inner edges of platform130 are fitted with guides, such as guides 149, 150, that comate withthe notches of a lip 92 of cuvette assembly 30. By using the guides, thecuvette assembly is precisely located on the platform and is rotatabletherewith.

As shown in FIG. 2, a test tube detection assembly 158 is held in acabinet 160 that is located one position ahead of the analyzingposition. The assembly comprises a pendulum 162 pivoted around a rod164. The pendulum normally swings into the path of test tubes 138, andin that position, causes a mercury switch 166 to be closed. When a testtube is positioned opposite assembly 158, pendulum 162 is moved to theposition shown in FIG. 2, thereby causing switch 166 to open. Assembly158 operates in a manner described hereafter so that the normaloperation of the system is interrupted if no test tube is present at aparticular position in ring member 136.

Referring to FIGS. 3 and 4, dispenser assembly 200 comprises a frame 202that includes a base member 203 and mounting plates 206, 207 and 208.

The dispenser assembly also comprises a probe holding assembly 212 thatincludes vertical support members 214 and 216. The vertical supportmembers are positioned by an upper arm 218 that is rotatably mounted bypins 220, 221. Likewise, the vertical support members are positioned bya lower arm 222 that is rotatably mounted by pins 224, 225. A tube 226is used to convey fluid to a probe assembly 260 that is mounted onsupport member 216.

Dispenser assembly 200 also comprises a vertical positioning assembly230 that includes an up-down solenoid 232 which operates a push rod 233having an upper end 234 along its longitudinal axis. Push rod 233 isrigidly connected to a piston 235 that operates in a cylinder 236. Thepiston is normally biased in an upward direction by a helical biasspring 237 that is held within the cylinder below the piston. As aresult, the probe holding assembly is normally positioned in theposition shown in solid lines in FIG. 3. (i.e., in the UP position).Cylinder 236 is rotatably mounted on plate 206 through a lower bearing238 and is rotatably mounted on plate 207 through an upper bearing 239.Adjustable stop members 240 and 241 cooperate with a bar 242 mounted onthe probe holding assembly in order to determine the lowermost positionof the probe assembly when it is positioned over the test tubes andcuvette, respectively.

Dispenser assembly 200 also comprises a horizontal positioning assembly244 that inclues a spiral spring 246 having one end connected to plate207 and the other end connected to cylinder 236. This spring normallybiases the probe holding assembly in the position shown in phantom inFIG. 4 (i.e., in the test tube position). I

Adjustable stops 248 and 249 are used to control the position of theprobe holding assembly when it is positioned over the test tubes and thecuvette assembly, respectively. Assembly 244 further comprises arotation solenoid 250 that operates a push rod 252 along itslongitudinal axis. Push rod 252 is connected through pins 255, 256 andarm 257 to a fixture 254 that, in turn, is

rigidly affixed to one side of cylinder 236.

Referring to FIGS. 5 and 6, the dispenser assembly also comprises aprobe assembly 260. The probe assembly comprises a stainless steelnozzle 262 that includes a front barrel 263, a rear barrel 264, and anend point 261. The front barrel has an inside diameter of 0.015 inchesand an outside diameter of 0.020 inches. The rear barrel has an insidediameter of 0.0l5 inches and an outside diameter of 0.032 inches. Thetotal length of the nozzle is 0.39 inches. As shown in FIG. 10, thenozzle is fitted into a tube 266 so that the rear barrel is completelyenclosed by the tube. A solder rod 267 is placed over tube 266 in thelocation shown in order to precisely locate tube 266 in correspondingnotch in support arm 216. Tube 266 is terminated in a beveled portion268 that comates with tube 226 in the manner shown in FIG. 3.

Applicant has discovered that the dimensions of the nozzle are criticalfor the efficient and accurate dispensing of organic liquids, such asblood serum. More specifically, applicant has discovered that the insidediameter of the nozzle should be between 0.010 inch and 0.020 inch. Ifthe nozzle diameter is substantially less than 0.010 inch, the nozzletends to clog with any foreign matter that is located in the system. Ifthe inside diameter of the nozzle is substantially greater than 0.020inch, two problems occur:

1. The velocity of the discharge is not sufficient to cause adequatestirring or mixing of the reagent fluid and blood serum.

2. The meniscus of the fluid at the end point of the nozzle becomesdifficult to control. For example, the lower portion of the meniscusmight break off, thereby decreasing the accuracy of the amount of fluidtransferred.

The outside diameter of the nozzle should be made as small as possibleconsistent with an appropriate degree of structural strength, therebyreducing the area of the nozzle wetted by the blood serum and holdingcarry over to a minimum.

The dispenser assembly also comprises a mixing assembly 270. Referringto FIGS. 3 and 7-10, the mixing assembly comprises a reagent or mixingliquid reservoir 272 that holds a reagent fluid or mixing liquid whichis mixed with samples held in test tubes 138 in order to preparespecimens for the various cuvette compartments. The reagent reservoircomprises a dip tube 273, a cover 274, and a transfer tube 275 that isconnected with the dip tube.

Referring to FIGS. 7-9, the mixing assembly also comprises amicrosyringe 280 having a capacity of 50 microliters. The microsyringehas a glass barrel 281 and a stainless steel tip 282 that define anouter cylinder 283. A hollow plunger 284 defining an inner cylinder 285is arranged to slide within the outer cylinder 283. Cylinders 283 and285 together define a cavity or chamber 286 having an inlet orifice orend opening 287 located at the end of tip 282 and an outlet orifice orend opening 288 located at the end of plunger 284. Tip 282 is connectedto tube 226, which, together with probe assembly 260 defines apassageway to the probe nozzle tip 261.

Referring to FIG. 9, the mixing assembly also comprises a macrosyringe290 having a capacity of 2,500 microliters. The macrosyringe comprises astainless steel tip 292 that is fitted into a glass barrel 291 which themacrosyringe are connected to a three way valve I 300 that comprises acase 301 and a valve element 302. The valve element defines channels303, 304 that may be interconnected to various inlets 305, 306 and 307.Plunger 284 has its outlet orifice 288 rigidly connected to inlet 306 ofvalve 300. As shown in FIG. 9, when the valve is in its discharge"position, it forms a passageway, together with tube 298, that extendsfrom outlet orifice 288 of microsyringe 280 to the inlet orifice 296 ofmacrosyringe 290. As shown in FIG. 10, when the valve is in its chargeposition, tube 275, together with the valve and tube 298, form apassageway that extends from the reagent reservoir 272 to inlet orifice296.

Referring to FIGS. 3 and 11-14, the dispenser assembly also comprises anoperating assembly 310. The operating assembly comprises a horizontalsupport bar 314 that rigidly connects barrels 281 and 291 of syringes280 and 290, respectively to the frame. Another horizontal support bar315 connects reservoir 272 to the frame. Assembly 310- also includes aremovable plate 311 that is connected to valve 300 and to plunger 294 ofmacrosyringe 290 through a fixture 326. Plate 311 is connected to acarriage 312 by means of screws (not shown). By merely removing thesescrews, the entire plate assembly shown in FIG. 12 may be removed. Thisis an important feature since it facilitates the changing of themicrosyringe, macrosyringe, and reser-' voir in order to run differentdeterminations. By removing one plate assembly and substituting another,the apparatus may be changed to accommodate a different determination ina matter of seconds. Plate 311 carries a stop member 313 that may beadjusted by mounting it opposite various multiple holes 313a in plate311. Member 313 controls the lower position of plate 311 by engaging amicroswitch 363a that is attached to the frame through a bracket 319.Plate 311 also carries another stop member 321 that engagesanother'microswitch 363b which controls the upper position of plate 311.Carriage 312 is adapted to move along a vertical shaft 316 that isconnected between base plate 203 and horizontal plate 317. The carriageis coupled to shaft 316 through linear bearings 318, 320 that areadapted to slide in a vertical direction along the shaft. The carriageis driven by a rack 322 that cooperates with a pinion gear describedhereafter.

Referring to FIGS. 11 and 14, the operating assembly further comprises aclutch assembly 327, that includes an electric motor 328 which has itsrotor connected to a clutch plate 330 through a shaft (not shown). Theclutch plate operates a valve drive plate 332 having stop facings 333,334 through a low coefficient clutch facing 336. Drive plate 332 ispinned by means of a hole 342 to a shaft 338 having a slot 339. Stopfacings 333, 334 cooperate with stop members connected to the framewhich prevent shaft 338 from turning through more than 90 of arc. Slot339 cooperates with a rib 340 of valve element 302 in order to move thevalve element between the discharge and charge positions shown in FIGS.9 and 10. The clutch plate also operates'a pinion drive plate 344 havinga slot 345 through a high coefficient clutch facing 346. A pinion gear348 is connected to the drive plate through a pin (not shown) that fitsthrough a hole 350 into slot 345. This arrangement allows the clutchplate to move through of arc before the pinion gear is moved. The entireclutch assembly is held together by a retaining plate 352, screws 353,springs 354, and nuts 355.

Referring to FIG. 15, the operating assembly also comprises a dispensercontrol circuit 360. The control circuit basically comprises a motorcontrol circuit 362 having microswitches 363a and 363b that are mountedon the frame adjacent the carriage. Stop members 313 and 321 on thecarriage engage the microswitches during the operation of the dispenser.The motor control circuit is used to control windings 364 and 366 thatform a part of motor 328. The motor control circuit controls thewindings by transmitting signals over conductors 367, 368 and 369.

The dispenser control circuit also comprises an updown solenoid controlcircuit 370 that is used to control a winding 372 of up-down solenoid232 by means of conductors 373, 374. The dispenser control circuitfurther comprises a rotation solenoid circuit 376 that is used tocontrol a winding 378 of rotation solenoid 250'by means of conductors379, 380.

The reference numbers in FIG. 15 identify components of the typedescribed in the following Table A:

TABLE A i Reference Number Type of Component 604 resistor 606 capacitor608 diode 609 solenoid winding 610 junction transistor 6ll thyristor 612field-effect transistor 6l6 triac 624 switch contact 626 switch wiper InFIG. 15, other reference numbers are used to identify componentsdescribed as follows in Table B:

In addition, in the FIG. 15, conductors are indicated by numbers from700-799. Like-numbered conductors are connected together.

The NOR gates shown in the drawings are conventional logic gates thatproduce one of two voltage levels at their output terminals in responseto voltages transmitted to their input terminals. When switched to theirone state, the gates produce a relatively high voltage at their outputterminals, and when switched to their zero state, the gates produce arelatively low voltage at their output terminals. 7

A preferred circuit for controlling the operation of the circuit shownin FIG. 15 is described in my related application identified above whichis incorporated by reference. Reference is made particularly to FIGS. 31

and 33 of that application which show the interconnection of conductors6CC1 10CC1, 713 and 763 shown in FIG. 15.

DISPENSER ASSEMBLY OPERATION The operation of the dispenser assemblywill now be described assuming that a test tube 140 and itscorresponding cuvette compartment 83 are moved into the position shownin FIGS. 3 and 4. It is further assumed that test tube 140 holds anaqueous solution such as blood or the like, and that air has beenremoved from the mixing assembly.

As previously mentioned, springs 237 and 246 normally bias the probeholding assembly in its up position over the test tubes (i.e., theposition shown in solid lines in FIG. 3 and in phantom in FIG. 4).Referring to FIGS. and 16, operation of the dispenser assembly iscommenced by the transmission of a negative pulse over the dispense line713 to the motor control circuit 362. In response to this signal, themotor control circuit produces signal D1 across winding 364 of motor 328in the manner shown in FIG. 16. In response to signal D1, motor 328rotates clutch 330, valve drive plate 332, shaft 338, and rib 340 ofvalve element 302 through 90 ofarc so that the valve element is moved tothe position shown in FIG. 10. As shown in FIG. 16, the rotation ofvalve element 302 requires approximately 1.16 seconds.

While valve element 302 is being rotated, up-down solenoid circuit 370transmits signal D3 (FIG. 16) to winding 372 of up-down solenoid 232.Referring to FIG. 3, in response to the D3 signal, solenoid 232 rapidlylowers push rod 233, thereby lowering end point 261 of probe assembly260 below the surface of the liquid held in test tube 140 to level F. Inother words, the probe holding assembly 212 is lowered to the positionshown in phantom in FIG. 3 (i.e., the charge position). By properlyadjusting stop member 240, end point 261 is located not more than 2millimeters below the surface of the liquid. Applicant has found thatthis is an important feature, since it reduces the amount of surfacearea of the probe nozzle which is in contact with the liquid.

After the probe assembly is in its charge position and after valveelement 302 has rotated to the position shown in FIG. 10, the pininserted in hole 350 of pinion gear 348 (FIG. 14) engages an end of slot345, thereby causing the pinion gear to rotate. When the pinion gearrotates, it drives rack 322 and carriage 312 in a downward direction(FIG. 11). Since carriage 312 is attached to plunger 294 and valve 300,the plungers of the syringes are pulled away from the syringe barrels,thereby enlarging the cavities defined by the syringes. In this mode ofoperation, a small amount of fluid is drawn from test tube 140 throughend point 261 of the probe assembly into nozzle 262. Normally, theamount of fluid is approximately 10 microliters. At the same time,reagent fluid is drawn from reservoir 272 through tube 275, valveelement 302, and tube 298 into the cylinder of syringe 290. In order toachieve the foregoing results, carriage 312 is moved downwardapproximately one-half inch in approximately 1.46 seconds. When carriage312 moves downward far enough to engage microswitch 363a (FIG. 15)signal D1 is terminated and the carriage stops. If larger quantities offluid are to be drawn into the probe assembly, carriage 312 may be moveddownward an additional amount, by repositioning stop member 313. Aftercarriage 312 has stopped in its lower position so that plungers 284, 294have stopped moving, the operating assembly causes nozzle 262 to beretained in the fluid for at least 0.1 second. After the 0.1 secondinterval has passed, D3 is removed from winding 372 of the up-downsolenoid 232 as shown in FIG. 16. At this time, spring 237 rapidlyaccelerates the probe nozzle away from the liquid in test tube in anupward direction. This is an important feature, since the rapid upwardacceleration causes the probe nozzle to break away from the liquid intest tube 140 without retaining a drop of liquid on the nozzle itself.The probe assembly continues to accelerate upward until it attains theposition shown in solid lines in FIG. 3.

After thecharged probe assembly is in its up position, rotation solenoidcircuit 376 causes signal D4 (FIG. 16) to appear across winding 378 ofrotation solenoid 250 (FIG. 15.) In response to the signal, solenoid 250drives push rod 252 toward itself (as shown in FIG. 4) thereby causingthe probe holding assembly to move from the position shown in phantom inFIG. 4 to the position shown in solid lines.

At the same time the probe holding assembly is rotating toward thecuvette, motor control circuit 362 causes signal D2 (FIG. 16) to betransmitted through winding 366 of motor 328 (FIG. 15). In response tothe signal, the direction of clutch plate 330 is reversed so that valveelement 302 is returned to its original position shown in FIG. 13. Thisoperation takes approximately 1.16 seconds.

While the valve element 302 is rotating to the position shown in FIG. 9,up-down solenoid control circuit 370 again impresses signal D3 acrosswinding 372 of the up-down solenoid 232 (FIG. 15). In response to thissignal, the end point 261 of the probe assembly is lowered intocompartment 83 of the cuvette to level G (FIG. 2). Level G is calculatedto be not more than 2 millimeters below the terminal level of liquidwhich will be in compartment 83 after the probe assembly is discharged.This terminal level is shown as level H in FIG. 2. As previouslyexplained, nozzle end point 261 may be lowered to exactly level G byadjusting stop member 241. This is an important feature, sinceexperience has shown that a liquid bubble will be retained on the probenozzle if the nozzle end point 261 is not extended slightly below theterminal liquid level. If the nozzle end point remains above this level,a bubble of fluid will be retained on the nozzle, thereby tending tocontaminate the next specimen prepared. Likewise, if the nozzle endpoint extends too far below the terminal level, an excessively largearea of the nozzle is wetted, so that an excessive amount of thespecimen fluid is carried over to the next compartment.

After valve element 302 has rotated to the position shown in FIG. 9, thepin in hole 350 of the pinion gear 348 engages the opposite end of slot345, thereby driving rack 322 and carriage 312 in an upward direction asshown in FIG. 11. As a result, plungers 284 and 294 are moved intobarrels 281 and 291 of syringes 280 and 290, respectively. This movementreduces the size of the cavities defined by syringes 280 and 290 so thatthe sample fluid located in probe assembly 260 is expelled into cuvettecompartment 83, and the reagent fluid held in cylinder 295 is expelledthrough tube 298, valve 300, plunger 284, cylinder 283 of microsyringe280, tube 226, and probe assembly 260 into cuvette cornpartment 83. Thecarriage continues to move upward until microswitch 363b is operated bystop member 321, thereby terminating signal D2 and stopping thecarriage. The foregoing method of discharge is an important feature,since the reagent fluid is passed through the microsyringe 280, tube226, and the probe assembly after the fluid sample from the test tubehas been expelled into the cuvette compartment. This operation purgesthese components of the sample fluid, thereby preparing the system tomix another sample with an additional quantity of the reagent fluid. Inorder to provide adequate purging, the amount of reagent fluiddischarged through the probe assembly should be at least times as greatas the amount of sample fluid discharged. The proper ratio of reagent tosample fluid is provided by adjusting the relative sizes of themicrosyringe and macrosyringe.

The curved bottom and angled sidewalls of cuvette 30 cause the fluiddischarged by the probe assembly to be mixed in each cuvette compartmentby a swirling action. After the sample and reagent fluid are completelydischarged, the resulting specimen in compartment 83 has risen to thelevel H (FIG. 2) which is l to 2 millimeters above the level of endpoint 261 of the probe nozzle. After carriage 312 has stopped in itsupper position, the operating assembly causes nozzle end point 261 to beretained below level H for at least 0.1 second. After this time intervalhas passed, the up-down solenoid control circuit 370 removes signal D3from winding 372 of the up-down solenoid 232. In response to the removalof the signal, spring 237 rapidly accelerates the probe assembly upwardand away from the specimen fluid in compartment 83. Thereafter, signalD4 is removed from winding 378 of the rotation solenoid 250. In responseto the removal of the signal, spring 246 moves the probe holdingassembly away from the cuvette to the position shown in phantom in H0. 4over the test tubes. At this point, the dispenser assembly is ready foranother cycle of operation as soon as another test tube and cuvettecompartment are moved into the dispensing position by the cyclingassembly.

Those skilled in the art will appreciate that the specific embodimentsdescribed herein may be altered and changed by those skilled in the artwithout departing from the true spirit and scope of the invention whichis defined in the appended claims.

What I claim is:

l. A dispenser for mixing and dispensing a sample liquid from a samplereservoir and a mixing liquid from a mixing liquid reservoir comprising:

first means for defining a first chamber having a first end opening anda second end opening opposite the first end opening,

second means for defining a second chamber having an inlet orifice;

third means for defining a first passageway between the second endopening and the inletorifice; fourth means for defining a secondpassageway between the inlet orifice and the mixing liquid reservoir;

fifth means for defining a third passageway between the first endopening and the sample reservoir; valve means for closing the firstpassageway and opening the second passageway in a first position and foropening the first passageway and closing the second passageway in asecond position; and

operating means for positioning the valve means in its first positionand for enlarging the size of the first and second chamberssimultaneously whereby a portion of the sample liquid is drawn into thethird passageway and a portion of the mixing liquid simultaneously isdrawn into the second passageway, said operating means also being forpositioning the valve means in its second position and for decreasingthe size of the first and second chambers simultaneously whereby theportion of the sample liquid is expelled through the third passagewayand the portion of the mixing liquid is expelled through the firstchamber and the third passageway so that the first chamber and thirdpassageway are purged by the mixing liquid.

2. A dispenser, as claimed in claim 1, wherein the valve meanscomprises:

valve means for defining a first inlet orifice, a second inlet orificeand a third inlet orifice that lead to a central chamber; and

valve element means rotatable within the valve case means for definingone or more channels, whereby the inlet orifices may be interconnectedthrough one or more of the channels by rotating the valve element meanswith respect to the valve case means.

3. A dispenser, as claimed in claim 1, wherein the first means comprisesthe barrel of a first syringe and the second means comprises the barrelof a second syringe.

4. A dispenser, as claimed in claim 3, wherein the operating meanscomprises:

a removable plate; and

means for connecting the first and second syringes,

the valve means, and the second reservoir to the removable plate,whereby the exchange of the syringes is facilitated.

5. A dispenser, as claimed in claim 3, wherein the third means comprisesa hollow first plunger adapted to move in the barrel of the firstsyringe, and wherein the second means comprises a second plunger adaptedto move in the barrel of the second syringe.

6. A dispenser, as claimed in claim 5, wherein the diameter of thebarrel of the first syringe is smaller than the diameter of the barrelof the second syringe.

7. A dispenser for mixing and dispensing a first liquid from a firstreservoir and a second liquid from a second reservoir comprising:

a first syringe barrel having a first end opening and a second endopening;

a hollow first plunger adapted to move in the first syringe barrel;

a second syringe barrel having an inlet orifice;

a second plunger adapted to move in the second syringe barrel; firstmeans for defining a first passageway between the second end opening andthe inlet orifice; second means for defining a second passageway betweenthe inlet orifice and the second reservoir; third means for defining athird passageway between the first end opening and the first reservoir;valve means for closing the first passageway and opening the secondpassageway in a first position and for opening the first passageway andclosing the second passageway in a second position;

first support means for connecting the first syringe barrel to thesecond syringe barrel;

second support means for connecting the first plunger to the secondplunger;

a motor;

clutch means driven by the motor;

first plate means located on one side of the clutch means for operatingthe valve means; and

second plate means located on the opposite side of the clutch means formoving the first support means with respect to the second support meansonly after the first plate means has turned through a predetermined arc,whereby the valve means is located in its first position as the firstand second plungers are withdrawn from the first and second syringebarrels whereby a portion of the first liquid is drawn into the thirdpassageway and a portion of the second liquid is drawn into the secondpassageway, and the valve means is located in its second position as thefirst and second plungers are moved into the first and second syringebarrels, whereby the portion of the first liquid is expelled through thethird passageway and the portion of the second liquid is expelledthrough the first syringe barrel, first plunger and the third passagewayso that the first syringe barrel, first plunger and third passageway arepurged by the second liquid.

8. A method of mixing and dispensing a sample liquid held in a samplereservoir and a mixing liquid held in a mixing liquid reservoir by meansof a first chamber having a first end opening and a second end openingand a second chamber capable of holding liquid, said method comprisingthe steps of:

removing all gas from the first and second chambers by filling the firstand second chambers with the mixing liquid;

connecting the first end opening of the first chamber to the samplereservoir;

connecting the second chamber to the mixing liquid reservoir;

enlarging the first chamber so that a sample portion of the sampleliquid is drawn into the first chamber;

enlarging the second chamber so that a mixing portion of the mixingliquid is drawn into the second chamber;

disconnecting the first chamber from the sample reservoir;

disconnecting the second chamber from the mixing liquid reservoir;

connecting the second chamber to the second end opening of the firstchamber; and

expelling the mixing portion of the mixing liquid from the secondchamber through the first chamber so that the sample portion of thesample liquid is expelled from the first end opening of the firstchamber and the mixing portion of the mixing liquid passes through andpurges the first chamber.

9. A method as claimed in claim 8, wherein the steps 10. A method, asclaimed in claim 8, wherein the step of expelling comprises the stepsof:

decreasing the volume of the second chamber; and

decreasing the volume of the first chamber.

P040511 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patentNo 43,817,425 Dated June 18, 1974 Inventor(s) MAX D. LISTON It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 1, line 7, kindly omit "now abandoned",

and substitute therefor -now U. S. Patent No. 3,748,044, issued July 24,1973.

signed and sealed this 15th day of April 1975.

Attest:

C. EiARSHALL DAJN RUTH C. MASON Commissioner of Patents AttestingOfficer and Trademarks

1. A dispenser for mixing and dispensing a sample liquid from a samplereservoir and a mixing liquid from a mixing liquid reservoir comprising:first means for defining a first chamber having a first end opening anda second end opening opposite the first end opening, second means fordefining a second chamber having an inlet orifice; third means fordefining a first passageway between the second end opening and the inletorifice; fourth means for defining a second passageway between the inletorifice and the mixing liquid reservoir; fifth means for defining athird passageway between the first end opening and the sample reservoir;valve means for closing the first passageway and opening the secondpassageway in a first position and for opening the first passageway andclosing the second passageway in a second position; and operating meansfor positioning the valve means in its first position and for enlargingthe size of the first and second chambers simultaneously whereby aportion of the sample liquid is drawn into the third passageway and aportion of the mixing liquid simultaneously is drawn into the secondpassageway, said operating means also being for positioning the valvemeans in its second position and for decreasing the size of the firstand second chambers simultaneously whereby the portion of the sampleliquid is expelled through the third passageway and the portion of themixing liquid is expelled through the first chamber and the thirdpassageway so that the first chamber and third passageway are purged bythe mixing liquid.
 2. A dispenser, as claimed in claim 1, wherein thevalve means comprises: valve means for defining a first inlet orifice, asecond inlet orifice and a third inlet orifice that lead to a centralchamber; and valve element means rotatable within the valve case meansfor defining one or more channels, whereby the inlet orifices may beinterconnected through one or more of the channels by rotating the valveelement means with respect to the valve case means.
 3. A dispenser, asclaimed in claim 1, wherein the first means comprises the barrel of afirst syringe and the second means compriSes the barrel of a secondsyringe.
 4. A dispenser, as claimed in claim 3, wherein the operatingmeans comprises: a removable plate; and means for connecting the firstand second syringes, the valve means, and the second reservoir to theremovable plate, whereby the exchange of the syringes is facilitated. 5.A dispenser, as claimed in claim 3, wherein the third means comprises ahollow first plunger adapted to move in the barrel of the first syringe,and wherein the second means comprises a second plunger adapted to movein the barrel of the second syringe.
 6. A dispenser, as claimed in claim5, wherein the diameter of the barrel of the first syringe is smallerthan the diameter of the barrel of the second syringe.
 7. A dispenserfor mixing and dispensing a first liquid from a first reservoir and asecond liquid from a second reservoir comprising: a first syringe barrelhaving a first end opening and a second end opening; a hollow firstplunger adapted to move in the first syringe barrel; a second syringebarrel having an inlet orifice; a second plunger adapted to move in thesecond syringe barrel; first means for defining a first passagewaybetween the second end opening and the inlet orifice; second means fordefining a second passageway between the inlet orifice and the secondreservoir; third means for defining a third passageway between the firstend opening and the first reservoir; valve means for closing the firstpassageway and opening the second passageway in a first position and foropening the first passageway and closing the second passageway in asecond position; first support means for connecting the first syringebarrel to the second syringe barrel; second support means for connectingthe first plunger to the second plunger; a motor; clutch means driven bythe motor; first plate means located on one side of the clutch means foroperating the valve means; and second plate means located on theopposite side of the clutch means for moving the first support meanswith respect to the second support means only after the first platemeans has turned through a predetermined arc, whereby the valve means islocated in its first position as the first and second plungers arewithdrawn from the first and second syringe barrels whereby a portion ofthe first liquid is drawn into the third passageway and a portion of thesecond liquid is drawn into the second passageway, and the valve meansis located in its second position as the first and second plungers aremoved into the first and second syringe barrels, whereby the portion ofthe first liquid is expelled through the third passageway and theportion of the second liquid is expelled through the first syringebarrel, first plunger and the third passageway so that the first syringebarrel, first plunger and third passageway are purged by the secondliquid.
 8. A method of mixing and dispensing a sample liquid held in asample reservoir and a mixing liquid held in a mixing liquid reservoirby means of a first chamber having a first end opening and a second endopening and a second chamber capable of holding liquid, said methodcomprising the steps of: removing all gas from the first and secondchambers by filling the first and second chambers with the mixingliquid; connecting the first end opening of the first chamber to thesample reservoir; connecting the second chamber to the mixing liquidreservoir; enlarging the first chamber so that a sample portion of thesample liquid is drawn into the first chamber; enlarging the secondchamber so that a mixing portion of the mixing liquid is drawn into thesecond chamber; disconnecting the first chamber from the samplereservoir; disconnecting the second chamber from the mixing liquidreservoir; connecting the second chamber to the second end opening ofthe first chamber; and expelling the mixing portion of the mixing liquidfrom the second chamber through the first chamber so that the sampleportion of the sample liquid is expelled from the first end opening ofthe first chamber and the mixing portion of the mixing liquid passesthrough and purges the first chamber.
 9. A method as claimed in claim 8,wherein the steps of enlarging the first chamber and enlarging thesecond chamber are performed simultaneously.
 10. A method, as claimed inclaim 8, wherein the step of expelling comprises the steps of:decreasing the volume of the second chamber; and decreasing the volumeof the first chamber.